Anatomy/Physiology

Question 1

Pinna

Answer 1

Gathers sound waves
Aids in localization
Amplifies sound 5-6 dB

Question 2

External Auditory Canal

Answer 2

approx 1 inch long

s shaped

Question 3

Mastoid Process of temporal bone

Answer 3

Bony ridge behind the auricle
Hardest bone in body-protects cochlea and vestibular system
Provides support to the external ear and posterior wall of the middle ear cavity
Contains air cavities which can be reservoir for infection

Question 4

Middle Ear Cleft

Answer 4

Middle ear cavity
Additus
Antrum
Mastoid air cells
Eustachian tube

Question 5

Ossicles

Answer 5

Ossicular chain- Malleus, Incus & Stapes

Malleus-TM attaches at Umbo

Incus-connector function

Stapes-smallest bone in the body
Footplate inserts in oval window on medial wall
Focus/amplify vibration of TM to smaller area, enables vibration of cochlear fluids

Question 6

Eustachian tube

Answer 6

Mucous-lined connects middle ear cavity to nasopharynx
Equalizes air pressure in middle ear
Normally closed, opens under certain conditions
As age- lengthens and becomes more vertical.

Question 7

Stapedius Muscle

Answer 7

Attaches to stapes
Contracts in response to loud sounds; acoustic reflex
Changes stapes mode of vibration; makes it less efficient and reduce loudness perceived
Build in earplugs..ish
Absent acoustic reflex could signal conductive loss or marked sensorineural loss.

Question 8

Central auditory system

Answer 8

VIIIth cranial nerve or Auditory Nerve
Bundle of nerve fibers (25-30k)
Travels from cochlea through internal auditory meatus to skull cavity and brainstem

Auditory Cortex
Wenicke’s area within temporall lobe of the brain
Sounds interpreted based on experience/association

Question 9

Typical hair cell

Answer 9

Kinocilium
Stereocilia
Cuticular plate

Question 10

Summary: How sound travels through the ear

Answer 10

Acoustic energy, in the form of sound waves, is channeled into the ear canal by the pinna. Sound waves hit the TM and cause it to vibrate, like a drum, changing it into mechanical energy. The malleus, which is attached to the TM, starts the ossicles into motion. The stapes moves in and out of the oval window of the cochlea creating creating a fluid motion or hydraulic energy. The fluid movement causes membranes in the Organ of Corti to shear against the hair cells. This creates an electrical signal which is sent up the auditory nerve to the brain. The brain interprets it as sound.